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FERNS
(PTERIDOPHYTES)
Ferns are vascular plants that do not produce seeds. Sexual reproduction
is accomplished by the release of spores, which develop in special structures
called sporangia (singular: sporangium). The sporangia usually occur in clusters
called sori (singular: sorus), found on the underside of “fertile” leaves. Fern
leaves, often called fronds, usually arise from underground stems (rhizomes).
The primary divisions of compound leaves are referred to as pinnae (singular:
pinna), and further divisions of pinnae are known as pinnules.
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Nephrolepis cordifolia (L.) Presl
Dryopteridaceae/Wood Fern Family
Common Names:
Synonymy:
Origin:
Erect sword fern, tuber sword fern, fish-bone fern, ladder fern,
Boston fern
Polypodium cordifolium L., Aspidium cordifolium (L.) Swartz
[also sometimes placed in Nephrolepidaceae, ladder fern family,
or Davalliaceae, sword fern family]
Tropics, perhaps pantropical
Botanical Description: Epiphytic, epilithic (on rock), or terrestrial in habit. Rhizomes
suberect, with spreading, orange-brown to pale brown linear scales, these with hairlike
tips; wiry, straw colored, scaly stolons usually present in great numbers, often producing
small, scaly underground tubers. Leaves (fronds) once pinnate, fertile and sterile fronds
similar in shape and size, to 1 m (3 ft) long and 7 cm (2.8 in) wide; petioles to 20 cm (8
in) long, with spreading, pale-brown scales; leaflets (pinnae) many, 40-100 on each side
of rachis (main stalk of frond); each leaflet (pinna) oblong-lanceolate with a deltoid lobe
(auricle) on upper side of blade base that usually overlaps rachis; leaflet margins entire to
slightly toothed; leaflet midvein glabrous above; rachis with two-toned (bicolored) scales
above, pale brown with distinctly darker point of attachment. Sori numerous at ends of
veinlets between leaflet midvein and margin, with kidney-shaped indusia (tissue covering
the sporangia).
KAL
KAL
NOTE: May be confused with native N. exaltata (L.) Schott, which never bears tubers,
has one-color rachis scales (sometimes obscurely bicolored), and has leaflet tips more
sharply pointed than those of N. cordifolia (Coile 1996a). Other Nephrolepis species in
Florida also with pointed leaflet tips and without the bicolored rachis scales of N.
cordifolia.
Scaly tubers
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Scaly rachis
Erect sword fern
Ecological Significance: Occurs most densely in partial or full shade of hammocks, as
far north as Florida Panhandle (Clewell 1985). Also noted as naturalized in Georgia
(Duncan and Kartesz 1981). Can spread aggressively in the landscape, tending to form
dense stands that displace native ground cover (K. A. Langeland, University of Florida,
personal observations). Said to thrive in common or even poor conditions and produce
dense crowns of long, drooping leaves (Bailey and Bailey 1976). By 1981 (Nauman),
noted as a widespread escapee from cultivation in central and south Florida. Reported
from conservation areas of Dade, Palm Beach, Martin, Collier, and Pinellas counties, in
pine rocklands, flatwoods, and marsh edges as well as in hammocks (EPPC 1996). Once
thought by some writers (e.g., Wherry 1964) to be native to southernmost Florida, but
many herbarium specimens of N. exaltata previously misidentified as N. cordifolia
(Nauman 1981). N. cordifolia also not described for Florida in earlier works (e.g., Small
1918a, 1918b), and presently distributed in the state without conformity to natural
boundaries such as the frost line (Nauman 1981). Natural populations in Old World
found in areas as remote as northwest Himalayas (Gaur and Painuli 1993). Origin in
New or Old World tropics still considered uncertain (Nauman 1993b).
Distribution: Most abundantly naturalized in peninsular Florida, from Gainesville south
(Nauman 1981). Documented by herbarium specimens from 23 counties: Escambia,
Leon, and Duval in north Florida, and on both coasts and in the interior from Citrus,
Marion, and Volusia south to Dade and Collier (Wunderlin et al. 1995).
KAL
Life History: Fertile all year (Wunderlin 1982). Spread by natural dispersal of spores and
by accidental movement of stolons, tubers, and rhizomes, particularly by dumping of
yard refuse. Tuber production apparently limited to plants growing in humus (Nauman
1981). Fronds of plants north of the frost line overwintering in protected areas or dying
back—the rhizomes, stolons, or tubers producing new fronds in spring.
Habit
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Tectaria incisa cav.
Dryopteridaceae/Wood Fern Family
Common Name:
Synonymy:
Origin:
Incised halberd fern
Tectaria martinicensis (Spreng.) Copel., Aspidium martinicense
Spreng., Aspidium macrophyllum Rudolphi
[sometimes placed in Aspleniaceae, or placed under
illegitimate family name of Aspidiaceae]
Mexico, Central and South America, West Indies
Botanical Description: Terrestrial or epilithic (on rock) in habit. Rhizomes stout, shortcreeping, with brownish black scales. Leaves (fronds) pale green, once pinnate, fertile and
sterile fronds similar in shape and size; petioles as long or longer than blades, pale brown
above, dark brown and scaly at base, pubescent on both sides; blades to 90 cm (35 in)
long and 60 cm (24 in) wide, with a large, deeply lobed terminal leaflet (pinna) and
below that, 3-6 pairs of mostly entire pinnae; each leaflet of the lowest pair with usually 1
large, downward-pointing (basiscopic) lobe. Sori in 1-several rows on lower surface of
leaflets between midvein and margin; indusia (tissue covering sporangia) round-reniform,
attached at 1 edge (not centrally attached).
NOTE: May be confused with native T. heracleifolia (Willd.) Underw., which has centrally attached (peltate) indusia; dark green, slightly shiny fronds, with all margins at least
shallowly lobed and on each of the basal pinnae at least 2 basiscopic lobes. Other Tectaria
species in Florida much smaller in size.
Ecological Significance: First noted in Florida in the late 1970s (Nauman 1978, Austin
et al. 1979), in a few localities. Since noted for several more localities in Dade and
Broward County tropical hammocks (D. Austin, Florida Atlantic University, 1997
personal communication), where it competes in the understory with rare native ferns,
such as the state-listed threatened species, T. heracleifolia. Thought by some to be of
uncertain origin (G. Gann, Institute for Regional Conservation, 1997 personal communication) or possibly native (Lucansky, University of Florida, 1997 personal communication), but appearing from best current evidence to be a recent introduction. Not described for Florida in earlier works (Small 1918a and 1918b, Long and Lakela 1971,
Lakela and Long 1976). By 1985 (Lellinger), noted as “rare to infrequent” in Dade and
Broward. Grown as a landscape plant (Lellinger 1985) and possibly escaped from cultivation via dumping of yard refuse (Ward, University of Florida, 1997 personal communication). Considered “often a weedy plant” by Standley (1927) in describing ferns of the
Panama Canal Zone, a plant “able to persist in partly denuded areas” of Barro Colorado
Island. Also noted by Kenoyer (1928) as remaining common in “pioneer forest” areas on
the island 50 years after abandoned agricultural cultivation.
Distribution: Widely distributed in its native range (Morton 1966). In Florida, found in
Dade County in Bill Fadowsky Park, Charles Deering Estate, Black Creek Forest, and
Hattie Bauer Hammock, and in Broward County in the Fern Forest Nature Area. Documented by herbarium specimens from these two counties (Wunderlin et al. 1995).
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Incised halberd fern
KAL
Life History: Fertile all year (Wunderlin 1982). Spread by natural dispersal of spores and
aided by dumping of yard refuse (D. B.Ward, University of Florida, 1997 personal
communication). Cold-sensitive tropical. Prefers moist to wet habitats (Standley 1927).
Occurs in Florida most often in shade of rocky hammocks. Able to hybridize—a known
cross, Pleuroderris michleriana (D. C. Eaton) Maxon, occurring in T. incisa’s Central
American range (Wagner et al. 1978), suggesting the potential for genetic swamping of
threatened and endangered native Tectaria.
KAL
KAL
In Fern Forest natural area, Broward County
Frond
Sporangia clusters
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Lygodium japonicum (Thunb.) Sw.
Lygodiaceae/Climbing Fern Family
Common Name:
Synonymy:
Origin:
Japanese climbing fern
Ophioglossum japonicum Thunb. ex Murray [sometimes placed in
Schizeaceae, ray fern family]
Eastern Asia, temperate to tropical
Botanical Description: Fern with climbing, twining fronds of indeterminate growth, to
30 m (90 ft) long; main rachis wiry, stemlike. Leafy branches off main rachis (constituting the pinnae) compound, triangular in overall outline, 10-20 cm (4-8 in) long and
about as wide. Leaflets (pinnules) lobed, stalked, with terminal lobes often dissected
(pinnatifid), basal lobes irregularly lobed or dissected; leaf-blade tissue pubescent below
with short, curved hairs. Fertile leaflets contracted in shape, with two rows of sporangia
along the leaf margin, which is enrolled to partially cover the sporangia.
NOTE: May be confused with L. microphyllum (Cav.) R. Brown, Old World climbing
fern, but its leaflets unlobed (usually), glabrous below, articulate stalked (leaving wiry
stalks when blade detached).
Ecological Significance: Present as a weed in the Philippines and considered a common
weed in Taiwan (Holm et al. 1979). Most frequently naturalized in north and west
Florida, in shady or sunny, usually damp, disturbed areas such as yards and roadsides, but
also in less disturbed edges of swamps, marshes, lakes, creeks, hammocks, and upland
woodlands. Can form tangled masses over ground cover and shrubs, its dense canopy
eliminating the underlying vegetation (Nauman 1993a). Reported forming sun-blocking
“walls” of fern in tributary floodplains of the Apalachicola River (L. C. Anderson, Florida
State University, 1997 personal communication), and smothering seedlings of overstory
tree species (K. C. Burks, Fla. Dept. of Env. Protection, personal observations). Introduced in 1932 as an ornamental (Gordon and Thomas 1994). Reported as weedy in
southern Alabama as well (Nauman 1993a).
Distribution: Occurs naturalized in the U.S. from the Carolinas through Georgia,
Florida, Alabama, Mississippi, and Louisiana, to Texas and Arkansas. In Florida, occurs
across north and west Florida and south into central Florida, with documented sightings
as far south as Hardee and Highlands counties (Fla. Dept. of Agriculture, unpublished
records), and Broward County (R. Pemberton, U. S. Dept. Of Agriculture, 1997 personal communication). Verified herbarium specimens collected from naturalized populations in 29 Florida counties (Wunderlin et al. 1995).
Life History: North of the frost line, leaflets die in winter but stalks of leaves usually
remain intact, providing a “ladder” for climbing stalks of new growth. Spores winddispersed, and perhaps carried in dust on moving objects such as vehicles. Thought to
prefer soils of circumneutral pH (Nauman 1993).
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KAL
KAL
Japanese climbing fern
At hammock edge, Gulf County
KAL
Fertile pinnae
Section of rachis, 2 pinnae
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Lygodium microphyllum (Cav.) R. Brown
Lygodiaceae/Climbing Fern Family
Common Name:
Synonymy:
Origin:
Old World climbing fern
Lygodium scandens (L.) Sw., Ugena microphylla Cav.
[sometimes placed in Schizeaceae, ray fern family]
Africa to Southeast Asia, south Pacific islands, Australia
Botanical Description: Fern with dark brown, wiry rhizomes and climbing, twining
fronds of indeterminate growth, to 30 m (90 ft) long; main rachis (leaf stalk above
petiole) wiry, stemlike. Leafy branches off main rachis (constituting the pinnae) once
compound, oblongish in overall outline, 5-12 cm (2-5 in) long. Leaflets (pinnules)
usually unlobed, stalked, articulate (leaving wiry stalks when detached); leaf-blade tissue
usually glabrous below; fertile leaflets of similar size, fringed with tiny lobes of enrolled
leaf tissue covering the sporangia along the leaf margin.
NOTE: May be confused with L. japonicum, whose pinnae are often twice compound
(see preceding pages).
RER
Ecological Significance: Considered a principal agricultural weed in Malaysia and
present as a weed in Vietnam (Holm et al. 1979). Reported from Florida natural areas of
Broward, Highlands, Lee, Martin, Palm Beach, and Sarasota counties (EPPC 1996). In
1993, infested 1,233 acres (11% of the area) of Jonathan Dickinson State Park and the
Loxahatchee National Wild and Scenic River, including many acres of cypress swamps
(Roberts and Richardson 1995). By 1995, infested 17,000 acres (12% of the area) of the
Loxahatchee National Wildlife Refuge (Palm Beach County), blanketing entire tree
islands and even clambering over sawgrass in standing water (Jewell 1996). Poses management problems for both wildfires and prescribed burns because growth into canopy
creates an avenue for fire to spread where swamp waters have usually provided a natural
barrier. Has caused loss of some canopy trees with such “crown” fires, as well as loss of
native bromeliads residing on tree trunks (S. Farnsworth, Palm Beach County, 1995
personal communication; Roberts 1996).
Section of rachis with pinnae
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Old World Climbing fern
Distribution: Center of dispersal in Florida reported by Beckner (1968) and Nauman
and Austin (1978) as Loxahatchee River Basin in southern Martin and northern Palm
Beach counties. Herbarium specimens now recorded from Broward, Collier, DeSoto,
Highlands, Lee, Polk, and Sarasota counties (Wunderlin et al. 1996). Widespread in Old
World tropics from Africa and India to Malaysia and in Australia from Ryukyu Islands
south to New South Wales (Singh and Panigrahi 1984, Tagawa and Iwatsuki 1979).
RER
RER
Life History: Wiry rhizomes able to accumulate into dense mats 1 m (3 ft) or more thick
above native soil (J. Street, Palm Beach County, 1996 personal communication). Vegetative growth and production of fertile pinnules continuous throughout year. Can germinate from spores in 6-7 days, with 5-month-old spores still having an 80% germination
rate (Brown 1984). Fertile pinnules usually produced where plant receives sunlight, with
such exposed locations also aiding windborne dispersal of the spores. Often establishes
first at pineland/wetland ecotone. Usually killed back by fire, but not eliminated
(Maithani et al. 1986).
In natural area, Martin County
Fertile pinnules
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